Performance of the rural health improvement scheme in reducing the incidence of waterborne diseases in rural Sarawak, Malaysia.

This study evaluates and discusses the impact of the rural health improvement scheme in reducing the incidence of dysentery, enteric fever, cholera and viral hepatitis in Sarawak, Malaysia, using data compiled from state and federal health department reports. This study suggests that from 1963 to 2002, water supply intervention contributed to a more than 200-fold decrease in dysentery and a 60-fold decrease in enteric fever. Variations in reporting of viral hepatitis during that period make it difficult to detect a trend. Cholera was still endemic in 2002. Cholera and dysentery outbreaks, occurring when rural populations relied on contaminated rivers for their water supply, suggested that sanitation intervention was not as effective in reducing waterborne diseases. Recommendations are made for successive one-component interventions focusing on catchment management to ensure protection of current and alternative water supplies.

Particle dispersion for further Cryptosporidium and Giardia detection by flow cytometry.

AIMS: The aim of this study was to overcome the analytical problems encountered during the detection of protozoans by flow cytometry resulting from particle compaction. METHODS AND RESULTS: Malvern Mastersizer (Malvern Instruments, Malvern, UK) was used to characterize the particle distribution of four different water samples and/or particle concentrates incubated with (i) low ionic strength solution or sequestring agent, (ii) anionic or non-ionic surfactants (iii) industry detergent formulations and (iv) physical treatment. The recovery of oocysts and cysts in seeded and treated particle concentrates was estimated by cytometry and microscopy. The decrease in ionic strength of the aqueous solution was most efficient in particle dispersion for different types of water. Moreover, samples treated with deionized water or tetrasodium pyrophosphate showed the highest recovery with more than 80% of the oocysts and cysts recovered. CONCLUSIONS: Chemical treatments that act by altering the ionic strength of the medium are the most efficient for all water types tested here but the overall detergency performance cannot be predicted for all water types. SIGNIFICANCE AND IMPACT OF THE STUDY: Flow cytometric detection has been replaced largely by immunomagnetic separation but the data recorded still have relevance in this technique as well as in molecular techniques requiring DNA or RNA extraction.

Influence of co-substrates on structure of microbial aggregates in long-chain fatty acid-fed anaerobic digesters.

AIMS: The purpose of this study was to investigate the influence of co-substrates, such as glucose and cysteine, on the structure of microbial aggregates in anaerobic digesters treating oleate, a long-chain fatty acid (LCFA). METHODS AND RESULTS: Transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) were used to examine the structure of microbial aggregates. Fluorescence in situ hybridization (FISH) techniques were also used to characterize and localize the different trophic groups present in the aggregates. Oleate was found to inhibit the methanogenic activity and formation of granular biomass in digesters. The addition of co-substrates, such as glucose and cysteine either singly or in combination, increased the methanogenic activity and formation of granular biomass. Glucose was more effective than cysteine in reducing the inhibition by oleate on the methanogenic bacteria and in enhancing the formation of granules. CONCLUSIONS: The addition of nutrient substrate, such as glucose and cysteine could decrease the toxicity of LCFA on anaerobic granulation. SIGNIFICANCE AND IMPACT OF THE STUDY: The results suggest that the addition of other substrates might decrease the toxicity of LCFA on the granulation of biomass in anaerobic digesters and enhance methanogenic activity. A combination of TEM, CLSM and FISH techniques provides a better tool for visualizing microbial aggregates and for differentiating and localizing different microbial groups within these aggregates.